Scientists at Auburn University are shifting their catfish vaccine development strategy to bring vaccines to farmers.
“We are developing more cost-effective killed-bacterin vaccines and exploring new ways to get vaccines to Alabama farmers,” said Timothy Bruce, assistant professor in Auburn’s School of Fisheries, Aquaculture and Aquatic Sciences in the College of Agriculture.
Many vaccines are developed by reducing how well a pathogen causes disease, such as a genetic mutation that makes the bacteria harmless but still able to stimulate an immune response in a fish or other animal. The resulting vaccine is then often patented and licensed to a company that seeks federal approval for the vaccine, but this process is costly and can take decades.
“Our frustration is extremely high — as is the catfish industry’s,” said Mark Liles, associate dean for research and graduate studies for Auburn’s College of Sciences and Mathematics. “We can produce a vaccine that when applied onto feed can protect fish against disease. The science has been successful, but what has not worked is the path to get these solutions to catfish producers. We need to find a different way to get Auburn University innovations to farmers!”
Catfish production is the largest sector in America’s $2 billion aquaculture industry, according to the USDA. However, each year Alabama catfish farmers lose millions of dollars in revenue to disease. A significant cause of catfish disease is a hypervirulent strain of Aeromonas hydrophila. This bacterial pathogen was first reported in the U. S. in 2009, and the evidence points to its introduction from Asian carp, with the disease resulting in over 40 million pounds of dead channel catfish to date in the State of Alabama alone, according to Liles.
Thanks to the support of the Alabama Agricultural Experiment Station, Liles led a team of researchers that developed a vaccine to protect catfish against Aeromonas hydrophila in 2012, and this patented vaccine was licensed to an animal health company but is still not commercially available.
Auburn researchers, working in collaboration with scientists at the USDA Agricultural Research Service’s Aquatic Animal Health Research Unit including Ben Beck, Benjamin LaFrentz, Craig Shoemaker and Miles Lange, have changed tack in favor of a killed-bacterin vaccine that is more cost-effective and can achieve more rapid regulatory approval.
A killed-bacterin vaccine is what most people think of when they think of a vaccine. A pathogen is grown, killed mechanically or chemically, and then introduced to a fish’s immune system to stimulate antibodies. If the fish is later infected with a live pathogen, its immune system is prepared. The first fish vaccines were developed in the 1940s using this method.
Importantly, killed-bacterin vaccines can be developed autogenously — meaning scientists take pathogens from a farmer’s pond and develop a vaccine with that specific pathogen. An autogenous vaccine could be approved through a more rapid process that includes an Alabama-licensed veterinarian, as opposed to federal USDA approval for a vaccine that requires a more lengthy regulatory approval process. This means that each state could develop its own vaccines to protect animals such as fish, poultry and livestock, but it limits this strategy to a state-by-state approach.
”Your pond, your bug, your vaccine,” said Bruce, “Your colleague, Joe, in Georgia? He can’t use that vaccine.”
Though the killed-bacterin method is nearly 100 years old, Bruce and Liles are exploring ways to better deliver the vaccine to fish through cost-effective formulations and by combining it with a probiotic.
“We are developing inexpensive ways to formulate the vaccine so that the bacterin can be orally delivered to fish and stimulate the immune response,” said Bruce. “Which can reduce the need for antibiotics and thereby promote sustainable aquaculture”.
The team found that a Bacillus probiotic, originally isolated from soybeans by AU Emeritus Professor Joseph Kloepper, is particularly good at killing fish pathogens like Aeromonas hydrophila. In a stroke of luck, adding this Bacillus probiotic to catfish feed also solves another problem for catfish farmers: anemia.
“A soy-based diet is actually a nutritional challenge for catfish,” said Liles. A soy-based diet, while relatively cheap, leaves catfish anemic because one of the components of soy meal phytic acid binds iron. Many farmers currently use catfish feed that has the enzyme phytase added to the feed to break down phytic acid and counter the anemia. Fortunately, the Bacillus probiotic naturally produces phytase, which can allow the fish to better absorb iron, and the probiotic also has other activities that helps to prevent diseases in fish.
“The probiotic will grow well on the soy feed that is used to feed catfish,” said Bruce. The Bacillus probiotic thrives on soy-based catfish feed, reducing how much needs to be added to the fish feed. The USDA grant that was awarded to Bruce and Liles funds research to test how the vaccine can work with or without the pathogen-killing Bacillus probiotic, thereby working in multiple ways to boost catfish immunity and prevent infection.
The use of vaccines and probiotics to prevent disease could have important ecological benefits for more sustainable aquaculture. Catfish farmers typically treat disease with antibiotics delivered on feed. But using antibiotics exposes both sick and healthy fish alike, and when fish begin to improve, catfish farmers have little incentive to continue feeding expensive antibiotics.
Like a person who doesn’t take all of their prescribed antibiotics, this allows surviving pathogens to potentially develop resistance to the antibiotic. “You’re doing evolution in your catfish pond,” said Bruce, “There are currently only three FDA-approved antibiotics for fish production. “It’s a struggle to get approval,” said Bruce. “And we need to provide farmers with cost-effective solutions to promote fish health instead of relying on antibiotics.”
“We need Alabama solutions for Alabama problems,” said Liles. “And need to find a way to produce autogenous vaccines and other animal health solutions that meet farmer’s needs”.
There is no source for autogenous vaccines in Alabama, although biotech firms that produce autogenous vaccines do exist in other parts of the U.S., including in Mississippi. “We need to change that,” said Liles. “I am hopeful that we can bring these solutions to market as a partnership with farmers. Tim and I are exploring how we can collaboratively develop an agriculture cooperative to accomplish this and would like to hear from people interested in working together toward this goal.”
Liles cites recent developments such as increased biotech investment in Alabama, the encouragement of the leadership at Auburn’s technology transfer office (IPX), and the interests of consumers in sustainably raised agriculture products as signs that conditions are right for the creation of an Agriculture Coop that could provide animal and plant health solutions to Alabama farmers. There are state and federal funding programs that could help fund an Agriculture Coop, such as Small Business Innovation Research grants that provide $4 billion annually to help U.S.-owned small business R&D efforts, as well as Innovate Alabama’s funding program, which has provided $17 million to date.
The research project “Investigation of probiotic potential to enhance vaccination in catfish” is funded by a $300,000 USDA’s National Institute of Food and Agriculture grant. The project is a partnership between Auburn’s School of Fisheries, Aquaculture and Aquatic Sciences SFAAS) in the College of Agriculture, and the College of Sciences and Mathematics (COSAM). Other grant team members include graduate students Marie Tan (SFAAS), Savannah Saegar (SFAAS), Emily Churchman (COSAM), Sol Llerena (COSAM), and Stacey LaFrentz (COSAM).
